Various glycoproteins (GP) are present on the surface of platelet membrane, and are involved in the expression of platelet functions. GPIb is one of the platelet membrane glycoproteins, and functions as a receptor of von Willebrand factor (vWF). GPIb is a heterodimer having a molecular weight of 160,000, wherein .alpha. chain and .beta. chain form a disulfide bond.
When vascular damages are caused, platelets quickly adhere to the lesion and form platelet thrombus by aggregation and the like. In forming the platelet thrombus, vWF plays an important role as an adhesive protein. It is considered that GPIb binds with vWF as a receptor thereof and activates or promotes adhesion and aggregation of platelets via vWF at said vascular lesion. In addition, the binding of vWF and GPIb functions to stop bleeding at the vascular lesion but also forms pathologic thrombus. Thus, GPIb is expected to be effectively used for the examination and diagnosis of vascular lesion, detection of pathologic thrombus, and treatment thereof.
Nevertheless, the use of isolated GPIb has not proved successful in artificial expression of the physiological activity as mentioned above. In other words, some idea in the aspect of formulation of pharmaceutical preparations is needed to practically use GPIb as a pharmaceutical agent or reagent.